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We are using physical disk on two of Guest operating systems. Is this a know issue? Do we need to have DPM 2010?

"One or more physical disks are attached to virtual machine 'Myserver'. Back up programs that use the Hyper-V VSS writer cannot back up volumes that are attached to virtual machines as physical disks. To avoid potential data loss, use another method to back up the data on the physical disks. If you restore the data on this virtual machine, make sure to check the data of the physical disk for integrity. (Virtual machine ID 8EF3C0CB-967D-4D67-B4D8-7B782C7AC07C)"

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What makes you feel like you shouldn't use VHD files? –  Jake Oshins Mar 19 '10 at 12:38

2 Answers 2

this is because the host OS (and DPM agent) don't have access to the partition which the VM is using, by design.

Not sure if this is supported in DPM 2010, but another option would be to switch back to static VHD files (not dymanicly expanding). I imagine there isn't a 'huge' difference in performance between physical drives and static VHDs anyway, but maybe you know better :P

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If properly set up, the overhead for static VHS files is single digit percentage wise - 3-4%. There is a whitepaper on that. Assuming Hyper-V R2.... in R1 that was a lot more. –  TomTom Mar 19 '10 at 7:18

I assume when you say you're using "physical disks" you mean you're doing pass-through disks from the parent partition to the VMs. When you do that, you lose the ability to do bare-metal-like backups of the VM (and that doesn't change with DPM 2010). If you want to do full VM backups, you need to use VHD files. With pass-through disks, your backups are going to be just like a physical server - push the DPM agent to the VM itself and do backups of the source data there. This is one of the downsides to pass-through disks (you end up in the same situation when you assign disks directly to the VM via iSCSI as well).

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